Guaranteed 3 Percent COLA for Seniors Act of 2015 Directs the Bureau of Labor Statistics of the Department of Labor to prepare and publish a monthly Consumer Price Index for Elderly Consumers that indicates changes over time in expenditures for consumption which are typical for individuals in the United States age 62 or older. Amends title II (Old Age, Survivors and Disability Insurance) (OASDI) of the Social Security Act to: